MYLNE, ROBERT (1734–1811), architect and engineer, was the eldest son of Thomas Mylne (d. 1763) of Powderhall, near Edinburgh, mason, eldest son of William Mylne (1662–1728), mason [see under Mylne, Robert, 1633–1710]. The father was city surveyor in Edinburgh, and, besides having an extensive private practice, designed the Edinburgh Infirmary, completed in 1745, and recently pulled down. He was apprenticed to the masonic lodge of Edinburgh 27 Dec. 1721, admitted fellow craft on 27 Dec. 1729, master in 1735–6, in which latter year he represented it in the erection of the grand lodge of freemasons of Scotland, and was grand treasurer from November 1737 to December 1755. He was elected burgess of Edinburgh on 26 March 1729. He died 5 March 1763 at Powderhall, and was buried in the family tomb at Greyfriars. By his wife Elizabeth Duncan he had seven children. A portrait by Mossman, painted in 1752, is in the possession of the family. A copy was presented to the grand lodge in 1858, and it is reproduced in Mylne's ‘Master Masons’ (p. 251). The old term ‘mason’ was dropped, and that of ‘architect’ adopted, during his lifetime.

Robert was born in Edinburgh 4 Jan. 1734, and began his architectural studies under his father. He was admitted ‘prentice as honorary member’ to the grand lodge on 14 Jan. 1754, and was raised to the degree of master-mason on 8 April of the same year. He left Edinburgh in April 1754 and proceeded to Rome, where he studied for four years. On 18 Sept. 1758 he gained the gold and silver medals for architecture in St. Luke's Academy in Rome—a distinction not previously granted to a British subject. The following year he was elected a member of St. Luke's Academy, but, being a protestant, a dispensation from the pope was necessary to enable him to take his place. This was obtained through Prince Altieri, himself a student of art. He was also made member of the Academies of Florence and of Bologna. He visited Naples and Sicily, and took careful drawings and measurements of antiquities. His notes were still in manuscript at the time of his death, though he was working on them with a view to publication in 1774. After travelling through Switzerland and Holland he reached London in 1759, bearing a very flattering recommendation from the Abbé Grant of Rome to Lord Charlemont (Hist. MSS. Comm. 12th Rep. x. p. 252). At the date of Mylne's arrival in London designs for the construction of Blackfriars Bridge were being invited. Mylne, though a stranger in London, submitted one, which was approved in February 1760. His choice of elliptical arches in lieu of semicircular gave rise to some discussion, in which Dr. Johnson took part in three letters in the ‘Daily Gazetteer,’ 1, 8, and 15 Dec. 1759, in support of his friend John Gwynn [q. v.] It is to the credit of those concerned that the acquaintance thus formed between Johnson and Mylne developed later into a warm friendship, despite this difference of opinion. On 7 June 1760 the first pile of Mylne's bridge was driven. The first stone was laid on 31 Oct. (view of ceremony, from a contemporary print in Thornbury, Old and New London, i. 205), and it was opened on 19 Nov. 1769. During the years of construction Mylne was often abused and ridiculed, and the popular feeling was expressed by Charles Churchill in his poem of ‘The Ghost,’ 1763 (p. 174). A view of the approved design was engraved in 1760; an engraved plan and elevation by R. Baldwin, a view of a portion of the bridge by Piranesi in Rome, and another by E. Rooker in London, were all published in 1766. Mylne's method of centering has been much commended, and his design has been frequently engraved. Despite the fact that the bridge was constructed for something less than the estimate, Mylne had to resort to legal measures to obtain his remuneration. The bridge was removed in 1868.

Among Mylne's other engineering and architectural works may be mentioned: St. Cecilia's Hall in Edinburgh, on the model of the Opera House at Parma, since used as a school, 1762–5 (view in Cassell's Old and New Edinburgh, i. 252); a bridge at Welbeck for the Duke of Portland, 1764; the pavilion and wings of Northumberland House, Strand, 1765; Almack's (now Willis's) Rooms in King Street, St. James's, 1765–6; house for Dr. Hunter in Lichfield Street, 1766; Blaise Castle, Bristol, 1766 (views in Neale, Seats, vol. iv. 1821, and Brewer, Gloucestershire, p. 104); the Manor House, Wormleybury, Hertfordshire, 1767; the Jamaica Street Bridge, Glasgow, in conjunction with his brother William, noticed below, 1767–72; offices for the New River Company in Clerkenwell, 1770 (elevation in Maitland, London, Entick, 1775, vol. i. plate 128); Clumber Park, Nottinghamshire, 1770 (view in Thoroton, Nottinghamshire, iii. 405); City of London Lying-in Hospital, 1770–3 (Maitland, ib. vol. i. plate 127); Tusmore House, Oxfordshire (plan and elevations in Richardson, New Vit. Brit. vol. i. plates 3–5); Addington Lodge, near Croydon, since 1808 the residence of the Archbishop of Canterbury, 1772–9 (ib. vol. i. plates 32–3); the Bishop of Durham's portion of the bridge over the Tyne at Newcastle, removed in 1873 (Wooler being the architect of the corporation of Newcastle's portion), 1774; house for himself at the corner of Little Bridge Street, 1780 (cf. Thornbury, 'Old and New London, i. 207), afterwards the York Hotel, taken down in 1863, and the ground now occupied by Ludgate Hill railway station; works at Inverary Castle, 1780 and 1806 [see Morris, Robert, fl. 1754]; bridge over the Tyne at Hexham, Northumberland, 1784; hospital in Belfast, 1792; Mr. Coutts's house in Stratton Street, Piccadilly, 1797; the east front of the hall of the Stationers' Company, 1800; Kidbrook Park, Sussex, about 1804 (view in Neale, Seats, iv. 1821). He made considerable alterations to King's Weston, Gloucestershire, and Roseneath Castle, Dumbartonshire (1786), and repairs to Northumberland House in the Strand, Syon House, Middlesex, and Ardincaple House, Dumbartonshire.

Two of Mylne's great engineering designs were that for the Gloucester and Berkeley Canal, which has recently been completed to Sharpness Point, and that for the improvement to the fen level drainage, by means of the Eau Brink Cut above Lynn, which after much opposition was carried out by Rennie in 1817. Mylne drew up many reports on engineering projects, on which he was consulted. In 1772, after the destruction of the old bridge over the Tyne at Newcastle, he chose the site for a new one (many of his suggestions as to improvement in the approaches have been carried out in recent years); in 1775 he sounded the harbour and bridge at Great Yarmouth; in 1781 he surveyed the harbour of Wells-next-the-Sea in Norfolk; and in 1802 the Thames as far as Reading. In 1783 he reported on the disaster to Smeaton's bridge at Hexham; in 1784 on the Severn navigation; in 1789 on the state of the mills, waterworks, &c., of the city of Norwich; in 1790 on the Worcester canal; in 1791, 1793, 1794, and 1802 on the navigation of the Thames; in 1792 on the Eau Brink Cut; in 1799 and 1802 on the bed of the Thames in London, with reference to the reconstruction of London Bridge; in 1807 on the East London water works; and in 1808 on Woolwich dockyard. He was unsuccessful in his design for the new London Bridge in 1800.

Mylne was appointed surveyor of St. Paul's Cathedral in October 1766, and held the post till his death. In the cathedral, over the entrance to the choir, he put up the inscription to Sir Christopher Wren, designed the pulpit and fitted up the building in 1789 for the visit of the houses of parliament (view among J. C. Crowles's collection to illustrate Pennant's ‘London,’ xi. 95, in Brit. Mus.), and again in 1797, &c., for the charity children. He was made joint-engineer (with Henry Mill [q. v.]) to the New River Company in 1767, sole engineer after Mill's death in 1770, and resigned the post in favour of his son, William Chadwell Mylne [q. v.], in 1811. In 1800 he erected an urn with inscription at Amwell, Hertfordshire, to the memory of Sir Hugh Myddelton [q. v.], projector of the New River. He was appointed surveyor to Canterbury Cathedral in 1767, and clerk of the works to Greenwich Hospital (where he executed improvements) in 1775.

He published in 1757 a map of ‘The Island and Kingdom of Sicily,’ improved from earlier maps (reissued, London, 1799). In 1819 an elevation was issued of the ‘Tempio della Sibylla Tiburtina,’ at Rome, restored according to the precepts of Vitruvius and drawn by Mylne.

He became a fellow of the Royal Society in 1767, and was an original member of the Architects' Club, founded in 1791. Mylne's architectural style was almost too thoroughly Roman to suit his time. He was the last architect of note who combined to any great degree the two avocations of architect and engineer. With his death the connection of the family with the ancient masonic lodge of Edinburgh, which had been maintained for five successive generations, ceased. He was admitted ‘prentice’ on 14 Jan. 1754, and raised to the degree of master-mason 8 April 1754. His name appears for the last time in 1759.

Mylne married on 10 Sept. 1770 Mary, daughter of Robert Home (1748–1797) the surgeon, and sister to Sir Everard Home [q. v.], by whom he had ten children, four of whom survived him. His wife died 13 July 1797. Mylne died 5 May 1811, and was, at his own desire, buried in the crypt of St. Paul's Cathedral, near to the remains of Sir Christopher Wren. For the latter years of his life he had resided at Great Amwell, Hertfordshire. His portrait, painted by Brompton in Rome in 1757, was engraved by Vangelisti in Paris in 1783. It is reproduced on a smaller scale in Nichols's ‘Literary Anecdotes,’ ix. 233. A drawing of him by George Dance and engraved by W. Daniell was published in 1810, and again in 1814 in Dance's ‘Collection of Portraits.’ Another portrait is in Mylne's ‘Master Masons.’ Among the satirical prints in the British Museum are two concerning Mylne. No. 3733, entitled ‘Just arriv'd from Italy The Puffing Phenomenon with his Fiery Tail turn'd Bridge builder,’ dated October 1760, represents Mylne perched on an abutment of the bridge, with the rival competitors and others down below, freely commenting on him. The plate was afterwards altered and the title changed to ‘The Northern Comet with his Fiery Tail &c.’ No. 3741, ‘The (Boot) Interest in the (City) or the (Bridge) in the (Hole),’ represents a conclave of architects, of whom Mylne is one. Some accompanying verses refer to the influence of Lord Bute (Boot) alleged to have been used in his favour. Mylne was reported to be of sharp temper, but he was always scrupulously just.

William Mylne (d. 1790), brother of Robert, was entered apprentice on 27 Dec. 1750, and was with his brother in Rome in 1755–6. He was admitted freemason in Edinburgh in 1758, and was deacon of masons in 1761–2 and 1765. He became architect to the city of Edinburgh, member of the town council, and convener of trades in 1765. On 27 Aug. 1765 he contracted for the erection of the North Bridge, part of the walls and abutments on the north side of which gave way on 3 Aug. 1769, when the work was already well advanced towards completion. Differences arose between the town council and Mylne respecting the increased expense of finishing the bridge, and the question was brought before the House of Lords in 1770. Terms were, however, agreed upon, and the bridge was completed in 1772 (view in Cassell's Old and New Edinburgh, i. 338). He afterwards removed to Dublin, where he effected great improvements in the waterworks of the city. He died 6 March 1790, and was buried in St. Catherine's Church, Dublin, where a tablet to his memory was placed by his brother Robert.